1. Field of the Invention
The present invention relates to an ejector and an ejector cycle device using the same. The ejector cycle device can be suitably used for a vapor compression type refrigerating cycle using an ejector.
2. Description of the Related Art
As for a vapor compression type refrigerating cycle using an ejector, there is proposed a vapor compression type refrigerating cycle as described, for example, in JP-B1-3322263 (corresponding to U.S. Pat. Nos. 6,477,857, 6,574,987) that employs a vapor/liquid separator and an ejector for flowing only liquid-phase refrigerant into an evaporator. Moreover, JP-A-2005-37093 (corresponding to US 2005/0011221A1) proposes a vapor compression type refrigerating cycle including a differential pressure valve that is located between a vapor/liquid separator and an evaporator and has a differential pressure between before and after itself controlled nearly proportionally to a differential pressure between before and after an ejector, and a check valve that is arranged in series with this differential pressure valve and allows refrigerant to flow only in a direction in which refrigerant flows from the liquid refrigerant outlet of the vapor/liquid separator.
However, one of problems of the vapor compression type refrigerating cycle using the above-mentioned conventional ejector is that when the performance of an ejector is degraded, in particular, in the case of low outside air temperature, the amount of refrigerant flowing through an evaporator decreases to degrade the performance of the evaporator. For this reason, it is demanded to provide a cycle construction in which even when the performance of the ejector is degraded, refrigerant flows through the evaporator.
Moreover, a vapor compression type heat pump cycle in which heat on a low temperature side is transferred to a high temperature side by the use of an ejector is described in U.S. Pat. No. 6,550,265. Here, an ejector type heat pump cycle is provided to switch two heat exchangers between the high temperature side and the low temperature side by the use of two four-way valves.
However, the heat pump cycle constructed of two four-way valves increases cost and also decreases the ease with which it is mounted.
Moreover, there has been known an ejector cycle device in which a nozzle portion of an ejector and a pressure reducing means separate from the nozzle portion are integrated with each other, thereby being reduced in size (e.g., JP-A-2004-44906 corresponding to U.S. Pat. No. 6,871,506).
In the cycle disclosed in JP-A-2004-44906, an ejector with which a variable throttle is integrated is connected to the downstream side of a radiator, an accumulator is connected to the downstream side of the ejector, the liquid-phase refrigerant outlet of the accumulator is connected to the inlet of an evaporator, and the outlet of the evaporator is connected to the refrigerant suction port of the ejector. Therefore, the amount of refrigerant drawn by the evaporator depends only on the suction capacity of the ejector. For this reason, when the difference between high pressure and low pressure of the cycle becomes small and hence the input of the ejector decreases, the suction capacity of the ejector decreases, and the flow rate of refrigerant of the evaporator decreases. In this case, the evaporator cannot fully exert a cooling capacity.